The present invention relates to an electric motor with a housing and slide bearings for supporting the rotor shaft for driving processing machines, especially refiners in which the rotor shaft has no shaft shoulders in the vicinity of the slide bearings. Such a design of the rotor shaft is necessary if a major axial displacement of the rotor takes place operationally or for maintenance purposes.
Refiners are wood comminuting machines for the production of paper, in which pieces of wood are shredded between two grinding discs. They are driven, as is known, for instance, from Canadian Pat. No. 10 18 379, DE-OS No. 25 10 852, U.S. Pat. No. 3,910,511 or DE-OS No. 25 22 349, by electric motors, the refiner disc being coupled or fastened to one end of the rotor shaft. Since the processing devices, for instance, cutters of the refiner serving for comminuting the wood wear and then must be replaced, the bearings of the electric motor must be designed so that they permit a relatively large axial displacement of the rotor at standstill. Before the refiner is set in operation, it is customary to let the electric motor run for a short time without being coupled in order to determine the direction of rotation. Since such motors generally have slanted slots there is a danger with this uncoupled operation that the rotor is axially displaced in an undesired manner, since no shaft shoulders are provided in the vicinity of the slide bearings.